We propose to study some aspects of the response properties of single cells in the dorsal cochlear nucleus (DCN) and inferior colliculus (IC) in light of the organization of connections within and between these nuclei. Electrical stimulation of the efferent fiber tracts will be used to distinguish the responses of principal cells from those of interneurons. Electrical stimulation of afferent fiber pathways will be used to study the interaction of separate sources of input at the single cell level. Multiple neuron recording and crosscorrelation analysis will be exploited to make inferences about the connectivity of interneurons and principal cells within a nucleus. Information about connectivity will be correlated with responses to acoustic stimuli and with anatomic location.